Research Paper GEOSPHERE Grand Canyon provenance for orthoquartzite clasts in the lower Miocene of coastal southern California 1 1 2 3 4 1 GEOSPHERE, v. 15, no. X Leah Sabbeth , Brian P. Wernicke , Timothy D. Raub , Jeffery A. Grover , E. Bruce Lander , and Joseph L. Kirschvink 1Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Boulevard, MC 100-23, Pasadena, California 91125, USA 2School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, Scotland, UK KY16 9AJ https://doi.org/10.1130/GES02111.1 3Department of Physical Sciences, Cuesta College, San Luis Obispo, California 93403-8106, USA 4Paleo Environmental Associates, Inc., Altadena, California 91101-3205, USA 14 figures; 6 tables; 2 sets of supplemental files CORRESPONDENCE: [email protected] ABSTRACT sandstones. Collectively, these data define a mid-Tertiary, SW-flowing “Arizona River” drainage system between the rapidly eroding eastern Grand Canyon CITATION: Sabbeth, L., Wernicke, B.P., Raub, T.D., Grover, J.A., Lander, E.B., and Kirschvink, J.L., Orthoquartzite detrital source regions in the Cordilleran interior yield region and coastal California. 2019, Grand Canyon provenance for orthoquartzite clast populations with distinct spectra of paleomagnetic inclinations and clasts in the lower Miocene of coastal southern Cal- detrital zircon ages that can be used to trace the provenance of gravels ifornia: Geosphere, v. 15, no. X, p. 1–26, https://doi. org/10.1130/GES02111.1. deposited along the western margin of the Cordilleran orogen. An inventory ■ INTRODUCTION of characteristic remnant magnetizations (CRMs) from >700 sample cores Science Editor: Andrea Hampel from orthoquartzite source regions defines a low-inclination population of Among the most difficult problems in geology is constraining the kilome- Associate Editor: James A. Spotila Neoproterozoic–Paleozoic age in the Mojave Desert–Death Valley region (and ter-scale erosion kinematics of mountain belts (e.g., Stüwe et al., 1994; House in correlative strata in Sonora, Mexico) and a moderate- to high-inclination et al., 1998). A celebrated example of the problem, and the subject of vigorous Received 12 December 2018 population in the 1.1 Ga Shinumo Formation in eastern Grand Canyon. Detrital contemporary debate, is the post–100 Ma erosion kinematics of the Colorado Revision received 15 May 2019 Accepted 30 July 2019 zircon ages can be used to distinguish Paleoproterozoic to mid-Mesoprotero- Plateau of western North America (e.g., Pederson et al., 2002), and especially zoic (1.84–1.20 Ga) clasts derived from the central Arizona highlands region of the Grand Canyon region (e.g., Flowers et al., 2008; Karlstrom et al., 2008, from clasts derived from younger sources that contain late Mesoproterozoic 2014; Polyak et al., 2008; Beard et al., 2011; Wernicke, 2011; Flowers and Farley, zircons (1.20–1.00 Ga). Characteristic paleomagnetic magnetizations were 2012; Flowers et al., 2015; Lucchitta, 2013; Hill and Polyak, 2014; Darling and measured in 44 densely cemented orthoquartzite clasts, sampled from lower Whipple, 2015; Fox et al., 2017; Winn et al., 2017). The erosion problem of the Miocene portions of the Sespe Formation in the Santa Monica and Santa plateaus is particularly well posed. It was a broad cratonic region that lay near Ana mountains and from a middle Eocene section in Simi Valley. Miocene sea level for most of Paleozoic and Mesozoic time (e.g., Burchfiel et al., 1992). Sespe clast inclinations define a bimodal population with modes near 15° During the Late Cretaceous–Paleogene Laramide orogeny, the Cordilleran and 45°. Eight samples from the steeper Miocene mode for which detrital orogen roughly doubled in width. The Colorado Plateau and southern Rocky zircon spectra were obtained all have spectra with peaks at 1.2, 1.4, and 1.7 Mountains thus underwent a transition from residing near sea level, as a ret- Ga. One contains Paleozoic and Mesozoic peaks and is probably Jurassic. The roarc Cordilleran foreland basin during the Late Cretaceous, to a mountain remaining seven define a population of clasts with the distinctive combina- belt residing at elevations of 1–2 km during Paleogene and younger time (e.g., tion of moderate to high inclination and a cosmopolitan age spectrum with Elston and Young, 1991; Flowers et al., 2008; Huntington et al., 2010; Karlstrom abundant grains younger than 1.2 Ga. The moderate to high inclinations rule et al., 2014; Hill et al., 2016; Winn et al., 2017). The key challenge posed by this out a Mojave Desert–Death Valley or Sonoran region source population, and framework lies in using thermochronological information on the unroofing the cosmopolitan detrital zircon spectra rule out a central Arizona highlands history, and the distribution of sedimentary source regions and corresponding source population. The Shinumo Formation, presently exposed only within a depocenters, to constrain erosion kinematics. few hundred meters elevation of the bottom of eastern Grand Canyon, thus Existing models of erosion kinematics of the region differ mainly in the remains the only plausible, known source for the moderate- to high-inclination role they assign to the modern Colorado River (ca. 6 Ma and younger) versus clast population. If so, then the Upper Granite Gorge of the eastern Grand more ancient drainage systems dating back to Laramide time. Despite the lack Canyon had been eroded to within a few hundred meters of its current depth of consensus, a significant and recent point of agreement, based primarily on by early Miocene time (ca. 20 Ma). Such an unroofing event in the eastern thermochronological data, is that a kilometer-scale erosional unroofing event Grand Canyon region is independently confirmed by (U-Th)/He thermochro- occurred in mid-Tertiary time (ca. 28–18 Ma) in the eastern Grand Canyon This paper is published under the terms of the nology. Inclusion of the eastern Grand Canyon region in the Sespe drainage region (Fig. 1; Flowers et al., 2008; Lee et al., 2013; Karlstrom et al. 2014; Winn CC-BY-NC license. system is also independently supported by detrital zircon age spectra of Sespe et al., 2017). This unroofing event (described in more detail in the next section) © 2019 The Authors GEOSPHERE | Volume 15 | Number X Sabbeth et al. | Grand Canyon provenance for lower Miocene of coastal California Downloaded from https://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/doi/10.1130/GES02111.1/4850318/ges02111.pdf 1 by guest on 22 October 2019 Research Paper Figure 1. Geologic reconstruction, based on McQuarrie and Wernicke (2005), show- ing the early Miocene positions of Sespe Forma tion depocenters in the Santa Monica and Santa Ana mountains with dominant paleoflow directions, and the extent of the Sespe Formation source re- gions, as inferred by Howard (2000, 2006) and Ingersoll et al. (2018), but including a portion of the southwestern Colorado Pla- teau, after Wernicke (2011). Stippled area inside zone of 28–18 Ma erosional unroofing delimits 30,000 km2 area potentially con- tributing detritus to the Piuma Member of the Sespe Formation. The four main regions of exposed orthoquartzite (purple) include: (1) Death Valley–Mojave region, with Lower Cambrian Zabriskie Forma tion (ZQ) and as- sociated Neoproterozoic orthoquartzites; (2) Grand Canyon region, with Shinumo Formation (SQ) of Mesoproterozoic age in eastern Grand Canyon (EG), and quartzitic portions of the Tapeats Formation (TQ) of Cambrian age in western Grand Canyon (WG); (3) central Arizona highlands Paleo- to Mesoproterozoic rocks including Mazatzal, Tonto, and Hess Canyon groups (MTQ) and Del Rio Formation (DQ); (4) Neoproterozoic– Cambrian orthoquartzites (including clasts recycled in Jurassic conglomerates) in the Caborca area of Sonora, Mexico (CQ) and Mesoproterozoic quartzites at Sierra Prieta (PQ) in NW Sonora. Proposed paleorivers discussed in text shown in blue dashed lines. K—Kingman, Arizona; N—Needles, California; AZ—Arizona; CO—Colorado; NM—New Mexico; NV—Nevada; UT—Utah. GEOSPHERE | Volume 15 | Number X Sabbeth et al. | Grand Canyon provenance for lower Miocene of coastal California Downloaded from https://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/doi/10.1130/GES02111.1/4850318/ges02111.pdf 2 by guest on 22 October 2019 Research Paper is relatively localized compared with erosion histories of adjacent regions to volcanic, metavolcanic, and metaquartzite clasts also abundant in the Sespe across orogenic strike to the SW and NE, also defined by thermochronologi- Formation), because it is both ultradurable and its potential sources are widely cal data. To the SE in the Arizona Transition Zone and Mojave-Sonora Desert exposed in the headwater regions of all proposed major paleodrainages tribu- region, unroofing to near-present levels occurred in Laramide time (ca. 80–40 tary to the Sespe basin (Fig. 1). The scope of our study includes characteristic Ma), with the exception of rocks tectonically exhumed by Tertiary extension remnant magnetizations (CRMs) from 44 samples from the Sespe orthoquartz- (Bryant et al., 1991; Fitzgerald et al., 1991, 2009; Foster et al., 1993; Spotila et ite clast population, collected from three well-dated Sespe exposure areas. We al., 1998; Blythe et al., 2000; Mahan et al., 2009). To the NE, in the Colorado compare these data with CRMs of some 700 samples from potential source Plateau interior, erosional unroofing occurred mainly after 10 Ma, presumably regions in the Death Valley–Mojave